Increase depth percept of upside-down cup
Assuming your model geometry is good (I can't really tell from the screenshot), it becomes mainly a lighting, material and environment problem.

Lighting:
If you are going for a photo-realistic look, use Cycles for rendering. It will handle lights and shadows in a more intuitive way.

Material:
Is it suppose to be a styrofoam cup? A porcelain cup? Glass? Set up the material for the cup accordingly. Styrofoam would be almost all diffuse, with a Sub-Surface Scatter component. Porcelain would be diffused white, with an added layer of highly glossy top coat. Glass would be, well, the Glass material node.

Environment:
If the cup material is reflective at all, you will need to set up the environment so that there is something to reflect off. After all, a mirror ball in a perfectly grey world will only look grey.  Multiple Plane Emitters is a good starting point, they can mimic lights shining through a windows.